How many transactions were started during the execution of the request?

I have a transaction. The code is

set implicit_transactions on
select getdate()
begin transaction
begin transaction
   select * from price p1, product p2 where p1.product_id = p2.product_id
rollback
   delete from PRODUCT where product_id = 100871
   select 100860,2,3,getdate(),null from PRODUCT
commit
drop table price

The question is how many transactions were started during the execution of the request? As I understand it, some people refer to this as a "nested transaction" although this is not official terminology.

So, from the server's point of view, were there 2 transactions started, or 1?

Solution

The answer is neither of those.

It is three: one rolled back, one committed, the last one hanging.

EDIT: Original version was wrong about select getdate

Quote from the docs: SELECT statements that do not select from a table do not start implicit transactions. For example SELECT GETDATE(); or SELECT 1, 'ABC'; do not require transactions.

As follows:

You switch on implicit_transactions, this means commands open and leave open a transaction, they do not auto-commit.
select getdate() does not open a transaction, as no table is referenced
begin transaction opens a transaction
begin transaction increments @@trancount to 2
select * from makes no change, would normally open a transaction
rollback rolls everything back
delete from opens, but does not commit, a transaction.
select 100860 does nothing
commit commits
drop table price opens and leaves hanging a transaction

What happens if implicit_transactions is off? The answer is also three transactions, all committed except for the explicit one which is rolled back

select getdate() does nothing.
begin transaction opens, but does not commit, a transaction.
begin transaction increments @@trancount to 2
select * from makes no change
rollback rolls everything back
delete from opens, and commits, a transaction.
select 100860 does nothing.
commit commits nothing
drop table price opens, and commits, a transaction.

Please note: rollback transaction without a semi-colon ; is dangerous, as the next word can be interpreted as a transaction name. An incorrect transaction name means nothing happens. This is why you should always terminate statements with a semi-colon.